Iran's threat to close the Strait of Hormuz shows the U.S. military's vulnerability to dependence on foreign oil, a retired admiral said in Chicago Wednesday.

The weakness of America's diplomatic leverage against Iran parallels strategic, tactical, and operational weakness in the military, Vice Admiral Dennis McGinn told about 60 people at the Midwest Energy Connection conference sponsored by the Association for Corporate Growth.

"We're hobbled in some way by the fact that our dependence on foreign oil causes us to worry that the price of oil on the global market is going to go up," said McGinn, a former aircraft carrier commander and naval strategist who now serves as president of the American Council on Renewable Energy.

"Every time the price of a barrel of oil goes up by 10 bucks, the military has to scramble in readiness accounts and come up with $1.2 billion to pay for that delta in the cost of fuel."

But strategic costs are much higher, McGinn said.

"At the strategic level, think about the fact that we have tens of thousands of wonderful men and women in uniform in all the services scattered around the globe, and in no small measure are they there because of our dependence on foreign oil, guarding that lifeblood of the world economy. There's a tremendous cost in dollars and unfortunately in lives as well.

"We are paying a price, not just with our taxes but with our young people."

McGinn serves with other starred officers on the Military Advisory Board of CNA, a not-for-profit research and analysis organization. That panel spent a year in 2008 studying military vulnerability to oil dependence.

"We came up with a unanimous finding," he said, "and that finding simply stated that America's energy posture constituted a serious and urgent threat to our national security, militarily, diplomatically and economically. And further, those who wished to do the U.S. harm could exploit this vulnerability, which is principally our reliance on fossil fuel."